Portfolio assessment has gained importance in the last twenty years and has been in use at different areas in education. Foreign language teaching is one of them. This study aims to find out the opinions of students on portfolio assessment. The study was implemented in a secondary school English preparatory class. As part of the study, portfolios and portfolio assessment activities were integrated into the program in a treatment group. The analysis of student responses showed that portfolio assessment is a fair method, compared to traditional assessments it is a more down-to-earth approach, it increases student responsibility and motivates students positively. On the other hand, student responses revealed some negative results, like portfolio studies take time, there is a need to include various types of a lot of tasks in portfolios, and self-evaluations, reviews and corrections of student work entail a lot of student and teacher effort.